A Basic Overview of the Underground Locators and The Challenges Faced

Published on by Jon Armstrong

Utility Location Services

With the rapid development of infrastructure and advancement in technologies, the utilities lying underground has increased immensely.

From electrical and telecommunications lines to sewage, gas and water pipes, everything lies underneath and locating them in the safest and non-invasive method has become more complex recently.

Accurate underground utility locating and mapping is essential not only for the crew’s wellbeing but also for the unforeseen benefits of companies as well.

The two most challenges faced in utility location services are: 

  1. Weak signal
  2.  Obstruction from other resource

Underground Utility Locating Methods:


Electromagnetic (EM) is emitted by underground utilities. Now as electrical lines carry their current, they generate their signals.

However, due to induction, EM signals are also produced by other lines which mean that the utility line reradiates due to the metal present in it.

Also note that as per the composition, the frequency of the reradiated signal varies extensively. Adjusting the locator to the accurate frequency is the major role of any utility location operator. 

Two types of Underground locating methods:

  • Active:

It involves identifying and locating the known utility’s route. Operator sends a definite frequency signal into the ground which is radiated back or connects the underground locator which helps in getting precise location. 

  • Passive:

This method is generally used for locating unknown lines. With the help of locator's receiver, the location service provider searches the EM signals radiated back which help in sweeping the area.

However, unlike the active location method, the passive method isn't able to differentiate between different types of utility lines. 

Different Types of Underground Locators:

Utility Locator
  • Single-frequency locators:

With a simple design and technology, this locator transmits a single high-frequency EM signal. This locator is highly effective in detecting lines on sites with fewer underground lines.

Nevertheless, it is not able to identify the depth of the utility or determine its specific kind. 

  • Multi-frequency locators:

It allows the underground locating operator to pick a frequency to locate and map utilities.

Although frequencies with low range are highly effective in discovering a specific line, its overall ability of detection is still lower than compared to the high-frequency line.

Often, an operator uses high frequencies to discover utilities and later move to low frequency to classify two different utilities. 

Challenges Faced in Underground Utility Locating:


Adjusting the signals transmitted by the locator is the most common answer to the underground line locating and mapping challenges.

Here, the operator needs to imply different techniques in altering the existing current’s flow or inducing a signal in the targeted line which helps the locator's receiver to detect it.

To detect the signal more effective, the operator might need to change the location or size of the antenna as well.

Below listed are some of the most common challenges faced in utility location services:   

  • Bad Insulation

Generally, these are one of the most difficult utilities to detect as their insulation deteriorates over time. This phenomenon usually occurs when the metal surface touches the soil.

Here, the metal surface area that touches earth is directly proportional to the degree of signal loss.

  • Near Other Utilities

When many utilities are established at one single point, it becomes difficult to differentiate between two lines. This phenomenon usually happens when a signal which is induced passes from the targeted utility to the one in close proximity instead of the transmitter. This challenge becomes more severe when two lines are parallel for an extended area.

In such situations, the bond between the two electromagnetic fields exhibit only one electromagnetic field which makes it impossible for the locator to distinguish between two utilities. 

  • Utilities Bonded with Each Other

In order to offer a common surface to redirect current to ground, the utilities are tied together. In such situations, the locator can’t stimulate an electromagnetic signal, making it tough to detect the signal that helps in identifying the location of the targeted utility.  

  • Composition

Unfortunately, locators are only able to detect the utility made of metal, i.e. electrically conductive material. Others which are made of terra cotta or plastic goes undetected by the locator. Even the corroded metallic line which hinders the flow of electron cannot be detected.  

  • Depth of Buried Utilities:

EM fields degraded when passes by a soil or any other conductive material. A thick soil layer between the locator’s receiver and utility line will obstruct the locator from locating specific line.



GeoScan Utility & Structural Investigation offers a complete suite of underground utility location services which helps in accurately detecting and locating underground utilities in a non-invasive and non-destructive manner. To further inquire about our services or know how we can help in your next project, feel free to get in touch with us today!

Author's Bio:


Jon Armstrong is the industry-leading operator specialises in the structural investigation and cable fault finding. He is closely associated with GeoScan Utility & Structural Investigation which is Dial Before You Dig accredited and with its extensive knowledge and latest technologies have helped many businesses to perform safe excavation. 


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